A resistance random access memory, or a “ReRAM,” is a non-volatile memory device employing reversible change in resistance in a thin film with application of electrical voltage bias across the film. In some ReRAM devices, application of the electrical voltage bias in one manner can cause decrease in the resistance of the thin film, for example, by formation of filaments that function as leakage current paths or by increasing a crystallinity of the thin film. Application of a different type of electrical voltage bias can cause reversal of the resistance of the thin film to an original high-resistance state, such as by removal of the filaments from the thin film or by decreasing the crystallinity of the thin film. In some other ReRAM devices, reversible change of resistance is achieved by a non-filamentary mechanism, i.e., via changes in resistance of the bulk material, when a certain electrical bias is applied to device electrodes. The bulk switching or area switching mechanism may allow better area scaling. An example of bulk or area switching cell is barrier modulated cell (BMC) in which vacancy concentration is modulated in a metal oxide material providing an increased resistivity upon reduction of oxygen vacancy in the material.
Thus, data can be stored in a ReRAM cell by changing the resistance of the thin film, which can be a solid-state material. The thin film is referred to as a memory film or a read/write film. Examples of ReRAM devices are described in World Intellectual Property Organization (WIPO) Publication No. WO2007004843 A1 to Hong et al. and U.S. Patent Application Publication No. 2013/0043455 A1 to Bateman.